I. Peter Martini

Use of micromorphology for palaeoenvironmental interpretation of complex alluvial palaeosols: an example from the Mill Creek Formation (Albian), southwestern Alberta, Canada

Abstract Field observations are often not sufficient for process-based interpretations of palaeosols, particularly where they form parts of thick aggradational pedocomplexes within alluvial successions. Under such conditions micromorphology provides genetic, temporal and spatial information on soil-forming processes that is critical to an understanding of past environmental conditions. Thick alluvial successions of the Albian Mill Creek Formation contain abundant evidence of pedogenesis, but few well-developed palaeosol profiles, and therefore, provide an ideal case study in which to demonstrate the usefulness of micromorphological data for palaeoenvironmental interpretation. The micromorphological features of greatest interpretive value are types of clay coatings and ferruginous segregations, structure and fabric. Papules, evidence of bioactivity and ferruginous concretions provide information on geomorphic surface stability and assist in reconstructing temporal changes in drainage conditions. While individual features can provide some palaeoenvironmental information, the relationships of features to one another and assemblages of features provides additional information when analysed hierarchically to establish a sequence of sedimentologic and pedogenic events. A common, recurring sequence of palaeoenvironmental events, subject to local variations, can be recognized throughout the Mill Creek Formation. The presence of illuvial clay requires that water percolated through the soil and that the soil periodically dried out so that the translocated clay was retained. Dark reddish clay coatings indicate clay illuviation under freely drained conditions, while pale-yellow and silty clay coatings suggest that phases of free drainage alternated with phases of poorly drained or saturated soil conditions. The presence of iron-depletion coatings, iron nodules and quasiferrans indicates that these units were at least periodically saturated, and the occurrence of multiple, overlapping phases within single thin sections demonstrates that redox conditions fluctuated, strongly suggesting development in the vadose zone. Recent soils containing similar assemblages of features develop under warm temperate seasonal climates. Alternating phases of well-drained and saturated conditions on the Mill Creek floodplains are attributed to changing sediment supply and local palaeogeomorphology rather than to any major regional climate change. This type of process-based, micromorphological analysis should have broad application in other complex, pedogenically modified alluvial successions and similar studies would lead to a more detailed understanding of ancient palaeoenvironments.

Neogene—Quaternary basins of the inner Apennines and Calabrian arc

The objective of this chapter is to review key evidence and genetic hypotheses pertaining to the Neogene—Quaternary basins of the internal (western) side of the Apennines and Calabrian arc (Fig. 22.1). The basins of the Northern Apennines will be treated first and they will be compared and contrasted with those of the Southern Apennines and Calabrian arc. Sediment terms such as clay, sand and gravel are generally used rather then rock terms, because most materials are uncemented or only slightly cemented.

Pedogenic and diagenetic influences on void coating formation in Lower Cretaceous paleosols of the Mill Creek Formation, southwestern Alberta, Canada

Abstract Pedogenic and diagenetic influences on void coating formation were studied in two paleosols from the Lower Cretaceous (Albian) Mill Creek Formation in southwestern Alberta, Canada, using detailed micromorphological, mineralogical and geochemical methods. The paleosols consist of alternating decimetre-scale beds of red, grey-green and variegated mudstone. Intermediate horizons (red and grey-green variegated mudstones) contain associations of pale yellow clay coatings, dark red clay coatings, Fe-depletion hypo-coatings and Fe-oxide quasi-coatings. SEM–EDX-ray analyses indicate that the dark reddish coatings are dominated by Si, Al and Fe, with subordinate amounts of K, Na, Ca, Mg and Ti. Pale yellow clay coatings have a higher Si content, and lower Al, K, Na, Ca and Fe contents relative to reddish coatings. Within the paleosol profiles, the distribution of clay minerals indicates: (1) an increase in discrete clay minerals downward, (2) a decrease in mixed layer illite-smectite downward and (3) an increase in chlorite upward. X-ray diffraction indicates that the pale yellow and dark red clay void coatings are polymineralic. Pale yellow clay coatings have a higher proportion of mixed layer illite–smectite and kaolinite, less chlorite and are less crystalline than dark reddish coatings. Despite a diagenetic overprint, including development of diffusion gleyans, degradation of organic matter, burial reddening, and probably some smectite illitization, both compositional and morphological gradients exist in the paleosol profiles and void coatings. These gradients are most likely related to depositional variations and to pedogenic development in the original soils under variable Eh–pH conditions in the presence of organic matter. Therefore, although the void coatings are altered (diagenetic features) their morphology, mineralogy and perhaps even some of their microchemistry is attributable to the presence of pedogenic precursors initially formed in soils similar to modern, temperate Alfisols and glossic soils.

Upper Pleistocene glacial valley-junction sediments at Pias, Trevinca Mountains, NW Spain

Abstract Sediments at Pias (Galicia) provide evidence of Upper Pleistocene glacial activities at a valley junction in the north-western mountains of Spain. The sedimentary sequence consists of lower, predominately fine-grained lacustrine deposits with few lonestones, overlain by poorly sorted, sandy gravels interstratified with massive diamicton deposited during mid-Weichselian times (MIS 3) (marine isotope stage 3). The lacustrine sediments were deposited in a glacial valley temporarily dammed by a confluent glacier. The presence of active ice is suggested by massive diamicton layers best interpreted as till, rafted sediments in lacustrine deposits and deformation structures indicative of loading and kettle formation. Frozen ground conditions are suggested by a few involution-like structures. The Pias area contains one of the few western-Spain sedimentary records of Upper Pleistocene glaciation at relatively low latitude (about 42°N) and low altitude (less than 1000 m a.s.l.). A southern dip of the Polar front to 40–45°N latitudes, as occurred during Last Glacial Maximum, could have cut moisture to the northern Fennoscandinavian ice sheets. At the same time, however, sufficient precipitations would have persisted in north-western Spain to sustain extensive ice caps and their outlets to elevations as low as c. 900 m a.s.l.

Cold-climate, fluvial to paralic coal-forming environments in the Permian Collinsville Coal Measures, Bowen Basin, Australia

Abstract The Middle Permian Collinsville Coal Measures of the northern Bowen Basin illustrate a range of cold to cold-temperate, coal-forming environments. Cold climate is indicated by Glossopteris flora in the coal measures, and by restricted marine fauna dominated by brachiopods and bryozoa in correlative marine sequences of the Back Creek Group which contains also abundant lonestones (dropstones). Sedimentation was characterised by an overall transgression, interrupted by local fluvial and coastal progradation in a shallow, epicontinental sea during a relatively quiescent tectonic period. Six sedimentary environments are represented: fluvial, fluvio-paralic, barrier-strandplain, back-barrier, tidal flat and open marine. The basal coal formed from peat of swamps of abandoned areas of gravelly braided streams, and is massive, dull, and with high ash (20%), low sulphur (1%) contents. Overlying coals developed from peats formed in fluvio-paralic and paralic environments, and thicker seams are generally brighter, with low to moderate ash (8–17%) and moderate to high total sulphur (1–6%) contents. Seams associated with fluvial influence show splits and high ash yield, while seams associated with coastal deposits show high sulphur levels (up to 21%). In contrast to reported models of coal-forming environments, no clearly defined deltaic or inter-distributary bay-fill sequences were identified in the area studied. Rather, vast freshwater wetlands backed low-gradient, progradational coasts locally having bars and barriers. The barriers were not prerequisites for substantial peat accumulation, although may have locally assisted peatland development by raising the profile of coastal equilibrium.

Geomorphology of the Boao coastal system and potential effects of human activities-Hainan Island,South China

The Boao coastal system along the eastern coast of Hainan Island is a dynamic delta-tidal inlet-barrier formed during the late Holocene. The delta developed inside a shallow lagoon barred by a sandy barrier with a narrow, shallow tidal inlet opening. Two major distributary channels separated by small islands characterize the delta. The lagoon is silting up receiving and trapping sediments from both the river and, in minor measure during storms, through the tidal inlet opening and barrier washovers. The barrier at the tidal inlet is highly dynamic and changes its form, accreting (migrating spit) against the inlet during fair-weather conditions and being eroded during storms and river floods. The delta has almost completely filled the lagoon and major concerns exist on the effect that ongoing large development plans may have on the environment. These concerns include the effect on floods and rate of siltation once banks of the islands have been stabilized and floodwater and sediment load are impeded from spreading over the lowlands, and the effect of increasing pollutant loads from the new facilities on the ecosystems of the increasingly restricting lagoon water and on the seashores.

The Hudson Bay Lowland: major geologic features and assets

The Hudson Bay Lowland is a vast (325,000 km2), flat (average slope 0.5 m/km) physiographic region of Canada located to the southwest of James Bay and Hudson Bay. It is underlain by Paleozoic and Mesozoic rocks and bounded by Precambrian terrains. Thin Pleistocene till sheets, locally deposited on fluted terrains mantle most of the Lowland, and they are overlain by thin marine and coastal Holocene deposits which have formed during the ongoing regression from an early post-glacial sea, the Tyrrell sea. The present shores of the James Bay and Hudson Bay are but one stage of development of such regressive sequences. More than 90% of the vast emerged Lowland is covered by one of the largest cold wetlands and peatlands of the world. Up to 3–4 m thick peats have developed in the last 5000 years in inland fens and raised bogs.

Wetlands of the Attawapiskat River mouth, James Bay, Ontario, Canada

The Attawapiskat River is one of the major rivers entering James Bay, Canada. Wetlands of the lower 12 km portion of the river were studied between the Cree Indian village of Attawapiskat and James Bay. This portion contains both freshwater, freshwater tidal and brackish/saline wetlands along a gradient downstream to the river mouth. Due to the high flow of fresh river water, salt marshes did not occur directly at the river mouth where the submergentPotamogetonrichardsonii and emergentSagittarialatifolia occurred. This association gave way inland from the river bank to a complex association ofHippuristetraphylla,Eleocharispalustris, andCarexpaleacea, all indicative of brackish conditions. Further inland, a salt marsh community occurred mainly withPuccinelliaphryganodes,P.lucida,Triglochinmaritima, andScirpusmaritimus. The freshwater tidal portion of the river was characterized by the following sequence from the river:Potamogetonrichardsonii →Sagittarialatifolia →Eleocharis,Hippuris,Carex spp. complex. In better drained areas on levees,Equisetum spp. were present giving way to aSalix —Alnus zone, and eventual boreal forest.

Landscape Influences on the Development of the Medieval–Early Renaissance City-states of Pisa, Florence, and Siena, Italy

The objective of this chapter is to analyze how the local landscape and environmental conditions influenced the evolution of the city-states of Pisa, Florence (Firenze), and Siena, primarily from the High (~1000–1300 AD) to Late Medieval Age and early Renaissance (~1300–1500 AD). The three cities are located in the province of Tuscany in the central north-western part of Italy (Fig. 13.1).

General considerations and highlights of low-lying coastal zones: passive continental margins from the poles to the tropics

Abstract This Special Publication presents 23 papers that examine comparable, predominantly siliciclastic coastal zones of low-lying passive trailing-continental margins (primarily east Americas) from polar areas to the equator. The objective is to establish similarities and major differences among them. This introductory paper outlines major contributions of the various papers, but will also highlight coastal differences and briefly add information not fully treated by others. This is done in three parts: (a) some basic concepts are stressed, such as the importance of ‘coastal zone’ (total landscape) in the north–south comparison and the variable climates; (b) a review is made of the component materials of the coasts, such as difference in sediments owing to source rocks, weathering and geological history (glaciations), and in flora and fauna such as burrowing organisms; and (c) a few classical examples are reported from warm zones, such as Galveston Island and the Sapelo Island marshes, but the focus is on less well-known environments of cold areas – those most impacted by climate change. Each component of the coastal zone can develop diagnostic characteristics, but the entire assemblage of sedimentary and biological features is what uniquely defines present environments and allows identification of ancient coastal zones.